A carrier is defined as a block of continuous spectrum over which wireless data is transmitted. For example, in Evolved Universal Terrestrial Radio Access (E-UTRA) Long Term Evolution (LTE) Rel-8 standard, a maximum carrier bandwidth of 20 MHz is specified. Carriers of smaller bandwidth (1.4 MHz, 5 MHz, 10 MHz, 15 MHz) are also defined in LTE Rel-8 allowing more flexible use of spectrum, especially when a continuous 20 MHz spectrum is not available. However, an E-UTRA compliant user equipment (UE) must have the capability to transmit/receive over a 20 MHz carrier.
Bandwidth aggregation increases the data rate of a wireless communication system. Bandwidth aggregation aggregates different spectrums (called carriers or component carriers) permitting communication over a wider spectrum. This achieves a higher data rate in both the downlink (DL) and uplink (UL). In LTE-Advanced Rel-10 standard, carrier aggregation is defined for up to 5 component carriers where each component carrier can be up to 20 MHz. Thus the aggregated bandwidth can be as wide as 100 MHz enabling a data rate five times that of the conventional LTE Rel-8 system.